High frequency receiver



Feb. 21, 1939. E-HABANNET Ax. 2,147,813

HIGH FREQUENCY REEIVER Filed Feb. 25, 195e K @sheets-sheet 1 HIGH FREQUENCY RECEIVER Filed Feb. 25,v 1936 2 Sheets-Sheet 2 AHORA/5y Patented F eb. 21, 1939 HIGH FREQUENCY RECEIVER Erich Habann, Berlin-Frohnau, and Felix Gerth, Berlin-Tempelhof, Germany, assignors to C. Lorenz Aktiengesellschaft, Berlin-Tempelhof,

Germany Application February 25, 1936, Serial No. 65,576 In Germany February 25, 1935 20 Claims.

It is known that the reception of oscillations of very high frequencies meets with diihculties, particularly in the range of waves of less than l m, wavelength. It is known to use for the reception so-called braking-held circuit arrangements wherein three-electrode-valves are used, operating according to the Barkhausen-Kurz principle. In this arrangement the electrons, being attracted .by the grid, are braked by the potential of the anode and oscillate around the grid. These circuit arrangements have the disadvantage, that the tubes are very small and are not adapted for frequencies over 100 megacycles. Furthermore it has become known to use gaseous discharge tubes of the sorcalled split-anodemagnetron-type for the reception wherein one magnetic eld is eifective in the direction of the heated lament.

The present invention refers to reception circuit arrangements using such split-anode-magnetrons, having special advantages over the prior ones.

The invention has for its object to create a receiving arrangement of this kind that shall be free from such disadvantages. More particularly the invention aims at employing tubes the dimensions of which are suitable for manufacture. To such end it makes use of a tube having a subdivided anode to which the oscillatory circuit is coupled symmetrically. Such tubes have been employed for the purposes of transmission. In order to enable them to be used for the purposes 4 of reception the operation is effected without the aid of an anode current. To such end the anode potential may be kept su'iciently low or the diameter of the sub-divided anode chosen accordingly great, the sharpness of resonance increasing if the diameter of the anode is made larger. No reception is possiblerif this diameter is smaller than a diameter of a definite magnitude.

The invention will be understood from the following description and be particularly pointed out in the appended claims, reference being had to the accompanying drawings in which- Fig. l is a diagram relating to the operation of arrangements as provided by the invention. Figs. 2 to 8 are diagrammatic representations of embodiments `of the invention. Fig. 2 represents a reception circuit arrangement in its most simple embodiment. Fig. 3 represents a similar reception circuitarrangement, having the cathode surrounded by a special grid. Figs. 4 and 5 represent heterodyne circuit arrangements, wherein the received signals are at first amplified (Cl. Z50-20) at high frequency and then rectified in another stage. Fig. 4a illustrates an embodiment wherein thetube has a grid for receiving an intermediate frequency. Fig. 6 shows a circuit including a high frequency braking field amplifier. Fig. 7 shows a tube having screening plates at the ends of the anode. Fig. 8 shows an arrangement having a tube with an anode consisting of four parts instead of two parts.

Like reference characters denote like or similar parts throughout the several views.

The electron tube R shown in Fig. 2 has a heated lament H and two cylindrical parts A forming an anode. The discharge space of the tube is in a well known manner under the action of a constant magnetic field whose lines of force run parallel with the lament A. Such magnetic field may be produced by electromagnets or in a given case by permanent magnets, as more fully explained with reference to Fig. 6. Connected to the anode A, A is a Lecher wire system L which is bridged over at a nodal point by a short circuiting Wire K. The anode potential is supplied to the middle of the wire K and in a given case over a high frequency choke Dr. In the anode potential circuit the receiving indicator 'I' is included which is shown purely diagrammatically. This indicator may be a telephone or an indicating instrument and may comprise in addition an amplifier'. Connected to the Lecher wire system L are the two halves of a receiving dipole D1.

vThis connection may be inductive or capacitive instead of being galvanic as shown.

The operation is as follows:

The .electrons emitted by the heated filament I-I are caused by the said magnetic field to follow a `closed or circular path so as to return to the filament or cathode. The period the electrodes necessitate for accomplishing this motion solely depends upon the strength of the magnetic eld. If now high frequency voltages occur at the anode A, A in consequence of the energy received by the system L and if the duration of a period accords with the period of time the electrons necessitate for their movement, these will no longer move in circular paths but in helical ones so as to reach the anode nally and cause a current in the indicating circuit. This mode of action requires that the electrons are in no wise able to reach the anode if no high frequency oscillations are received. The anode potential must accordingly always be below a value which in the state of rest would cause an anode current. Magnetism and frequency must be subject to the corelation }=0.3 10FI H, where f is the frequency in cycles and H the magnetic field intensity in gausses. 'Ihe magnetism given by this formula is the magnetism of resonance. 'Ihe diameter of the anode A, A should in any case be greater than 1', this value r being defined by the relation 1-=2 where 1" is in millimeters and k in meters. In practice an anode diameter has proved to be suitable which is ten times the above defined minimum diameter. The larger the anode diameter the better the conditions with respect to making the electrons move in helical paths, but the greater must be also the extent, to which the received frequency and the resonance magnetism accord with each other. Since the resonance magnetism determines the received frequency in a definite single-valued manner system L may be adjusted to any of the possible resonance positions, no ambiguity being entailed in this way. The mode of oscillation of the system L is thus determined by the choice of the resonance magnetism.

By plotting the resonance magnetism Q in dependence upon the anode potential V the curve Q shown in Fig. l is obtained. It will be seen from this representation that the resonance magnetism is constant only in a range from the origin O to the value V1 and will then increase considerably in accordance with increasing values of V. The invention only makes use of the range O, V1, that is, the range within which the resonance magnetism is constant and no anode current is flowing. From the indicated relations it follows that the arrangement is adapted for use with ultra short waves, as in the case of low frequencies the dimensions of the tubesV become unhandy, while as regards the reception of ultra short Waves the arrangement has the advantage that tubes of normal dimensions may be employed so that the construction thereof will not meet with diniculties. Also no harmful high internal valve capacities occur, that is, capacities which again and again have proved to be a bar to using the circuit arrangements customary nowadays.

The sensitiveness of the arrangement can be increased considerably by surrounding the filament H with a so-called withdrawal grid G, as shown in Fig. 3. Such a grid is a helical or spiralshaped structure arranged in close proximity to the filament and having a slight positive potential with respect to the filament or cathode.

It will thus be necessary to calculate the anode potential on the basis of the grid potential and to use this basis also for calculating the dimensions of the anode cylinder. In other words, the grid is to be considered as a large surface cathode with respect to the oscillations of the electrons.

It is advantageous to limit the region of the magnetic lines of force to the space which there is between grid and anode. This may be performed by constructing the terminal lugs of the magnets accordingly or by providing that space with a magnetic screening.

The advantage that the system L need not be adjusted to the first nodal point but may be adjusted to any one of the succeeding nodal points enables the arrangement to be set oscillating to a long wave. In this state by .heating the filament sufficiently the arrangement may be caused to cscillate, whereas by heating it less the arrangement may be brought to be on the point of the oscillations beginning to set in. System L in such case is to vibrate in multi-wave fashion, viz. rst in accordance with the fundamental wave, that is, as a transmitter, and in the second place in accordance with a harmonic vibration equal to the received high frequency. The produced high frequency and the received high frequency thus are here in a harmonic ratio to each other. In each case the received high frequency is modulated. rI'he well known phenomena of superregenerative operation or of beat reception in the case of superheterodyne reception then occur. Depending upon the adjustment of the arrangement both these effects can be produced.

In the case of audible reception and attenuated waves it seems best to use a voice frequency alternating potential instead of the continuous anode potential. 'Ihe amplitude of this alternating potential is to be so chosen that no anode current is flowing Whenever there is no reception.

It may be mentioned here that the tubes show all the effects the more distinctly the freer they are of gases.

In the case of directly heated cathodes the small electric field which the heating current generates in the filament may be disturbing. As shown in Fig. 7 this is avoided by so disposing screening plates AS at the face ends of the anode cylinder A, said plates being kept at a negative potential by means of the potential source U, in order to close the discharge space. Preferably such plates are also given a potential difference with respect to each other and in such a manner that the field influence of the filament H is compensated.

In order to produce in a convenient manner the great magnetic field intensities necessary for the reception it is suitable to provide for the airgaps between the anode cylinder and the said magnets to be small. It is also advantageous in this regard to make the length of the anode cylinder equal to the diameter thereof or smaller than this diameter.

Instead of a two-part cylinder A. A a fourpart cylinder according to Fig. 8 is to be applied wherein the parts AI and A2 are connected by short circuit clamps BI and B2. The connection of the Lecher system L is effected in the middle of these short circuit clamps.

The described arrangement because of its sharpness of resonance and the distinctness of the received Wave is also a good wavemeter for ultra short Waves.

As is well known it is hardly possible to amplify the arriving high frequencies. Therefore improvements such as disclosed in Figs. 4 and 5 are helpful, which aim at increasing the sensitiveness of the receivers shown in Figs. 2 and 3. To such end the receivers are completed by leading an intermediate frequency to the tube R and taking the resultant current from the anode lead which is common to the parts of the split anode. The modulation of the arriving Wave is in this way transferred directly on to the intermediate frequency which then is amplified and rectified.

The arrangement represented in Fig. 4 has an intermediate frequency oscillator Z connected to the lead +A of the continuous anode potential, the device Z generating for instance a 1000 meter wave. This intermediate frequency in view of the statements given with respect to Figs. l to 3 can only flow when the system is receiving high frequency oscillations. I'o such end in addition to a proper choice of the magnetic eld strength care is to be taken that the impressed amplitude of the intermediate frequency be not beyond a predetermined value. This value is the smaller the greater the additional continuous anode potential. When such an intermediate frequency alternating potential is applied to the anode the continuous anode potential may be dispensed with. The use of such a continuous anode potential, upon which the alternating potential of intermediate frequency is superposed, is however advantageous inasmuch as it increases the output power. The intermediate frequency thus becomes modulated in accordance with the low frequency modulation of the received high frequency. The modulated intermediate frequency is by the circuit S conveyed to an amplifier N. After rectifying this modulated intermediate frequency, the resulting low frequency is led to the indicator T. The derived intermediate frequency is of the same frequency as the impressed intermediate frequency, but is modulated although the impressed intermediate frequency is modulated.` The fact that this modulation in the case of modulated ultra short waves received in the manner described with respect to Figs. 1 to 3 is effected by these ultra short waves directly and is simply transferred onto the intermediate Vfrequency involves a knowledge which is a basis of the invention.

The intermediate frequency instead of being conducted to the anode lead may be conducted to a special grid G2 provided in the tube R as shown in Fig. 4a.

It is especially advantageous however to impress the intermediate frequency on the anode members A, A and in phase opposition, as is shown in Fig. 5. It will be seen that here on reception there is pulsing in the circuit S a current of double the number of cycles of the intermediate frequency, the intermediate frequency being impressed on a coil E arranged to bridge over the Lecher wire system L in the current minimum. Also this current in S can only arise if the ultra short wave, received by the dipole D1, in conjunction with the appertaining resonance magnetism admits the flowing of anode currents. Owing to the fact however that the intermediate frequency .impressed on coil E is very different in the number of cycles from the modulated frequency at S, a disturbing and purely spatial infiuence on E and S is avoided here.

It may be mentioned that the circuit S in the case of Figs. 4 and 5 and also with any other arrangements of this kind may also be tuned to harmonics of the fundamental frequency.

On the transmitting side the ultra short wave need only be given the basic signal modulation, although it is possible to provide for an intermediate frequency modulation at the transmitter also, that is, modulation of a carrier that in its turn acts to modulate the carrier proper. If the conditions are proper and the intermediate frequency of a transmitter accords with that of the receiver peculiar effects of resonance character may be expected. This is especially so with respect to Fig. 5 if the intermediate frequency of the transmitter accords with the high frequency resulting in circuit S or if these twor frequencies are in a harmonic ratio to each other.

Fig. 6 represents a circuit arrangement wherein a transmission gain is effected in connection with detector circuit arrangements such as shown in Figs. 2 and 3. According to Fig. 6 a three-electrede-valve is interconnected ahead of the splitanode-magnetron, said valve operating, e. g., as a feedback circuit arrangement or, as shown on the enclosed drawings, in a braking eld circuit arrangement, wherein the grid Bg of the threeelectrode-valve B is kept at a positive potential and wherein the electrons being thus attracted are braked by the field of the anode Ba. Such braking field circuit arrangements are known per se. According to the present invention an amplification of the received high frequency is effected in this tube and this high frequency is rectified in the devices according to Figs. 2 and 3. By this arrangement the good amplifying characteristics of the known braking field amplifier as well as the great selectivity of the devices of Figs. 2 and 3 are obtained.

To a dipole D1 (Fig. 6) an electron tube B is connected to operate in braking-field connection. The high positive grid potential is supplied to this tube over a choke Drl. The anode potential, which is less than this grid potential, arrives over a choke Dr2. The potenials are so chosen that the tube B shall effect an amplification. The high frequency is not rectified in tube B. Our tube R is with respect to high frequencies connected to tube B. Blocking condensers C are arranged to prevent the continuous grid and anode potentials from influencing tube R. The connecting lines are preferably constructed as high-frequency transmission lines in order to provide for a good voltage transmission from one tube to the other. Tube B has lead-ins on both sidesv of each electrode in order to avoid junctions at the points of connection to the lead-ins. Two magnets M are arranged to produce the magnetic field acting as stated on the discharge space of tube R. These magnets are shown displaced with respect to the position they have in realty. Their true position is such that their lines of force extend along the axis of the tube R.

Our tube serves to select the desired reception frequency from the high frequency mixture that has been amplified in tube B. The rectification effect being extremely sharply dependent on frequency, a very efficient filter action is obtained.

Instead of the braking-field tube B any other tube arranged to operate in a disattenuating connection may be employed, that is to say a tube in feedback connection will be equally suitable.

Separate leads may of course be provided on the one hand for supplying the continuous anode potential and on the other hand for taking the low frequency.

What is claimed is:

1. A high frequency receiver comprising an electron tube having a split anode, an oscillatory circuit connected symmetrically to this anode, a cathode cooperating with said anode, a source of current connected with said cathode, means for producing a magnetic field adapted to influence the discharge space of this tube, the intensity of said anode a potential so related to the dimenrotation frequency of electrons under the inuence of this field equals the frequency of the received oscillations,l and means for applying to said anode a potential so related to the dimensions of said anode and the intensity of said magnetic eld that no anode current flows in the absence of received oscillations.

2. A receiver according to claim 1, wherein the split anode is a cylinder of a diameter whose magnitude expressed in millimeters is larger than twice the wavelength of the received waves expressed in meters. v

3. A receiver according to claim 1, wherein the split anode is a cylinder of a diameter whose magnitude expressed in millimeters is twenty times the wavelength of the received waves expressed in meters.

4. A receiver according to claim 1, wherein the oscillatory circuit comprises a Lecher wire system.

5. A receiver according to claim 1, wherein the oscillatory circuit comprises a Lecher wire system, and means for tuning said Lecher wire system to a frequency which is a submultiple of the received frequency.

6. A receiver according to claim 1, wherein the electron tube has a Withdrawal grid between said anode and said cathode and means for causing said grid to have a positive potential with respect to said cathode.

7. A receiver according to claim 1, wherein the electron tube has a withdrawal grid between said anode and said cathode and means for causing said grid to have a positive potential with respect to said cathode and wherein means are provided to limit the influence of the magnetic field to the space between this withdrawal grid and the anode.

8. A receiver according to claim l, wherein the electron tube has a withdrawal grid between said anode and said cathode, means for causing said grid to have a positive potential with respect to said cathode andfscreening plates closing the discharge space of this tube and having a potential difference with respect to each other.

9. A receiver according to claim l, wherein the split anode is a cylinder Whose length is smaller than its diameter.

10. A receiver according to claim 1, characterized in this, that the oscillation circuit comprises a Lecher system, a bridge over said Lecher wire system in one of the nodal points which is distant from the connection point more than half a wave length,

l1. A receiver according to claim 1, wherein said means for applying a potential to said anode comprise a source of alternating voltage connected to said anode.

12. A high frequency receiver comprising an electron tube having a split anode, an oscillatory circuit `connected symmetrically to this anode, a cathode cooperating with said anode, a source of current connected with said cathode, means for producing a magnetic eld adapted to influence the discharge space of this tube, the intensity of said magnetic eld being such that the rotation frequency of electrons under the influence of said field equals the frequency of the received oscillations, means for applying to the anode a potential so related to the intensity of said magnetic field and the dimensions of said anode that in the absence of received oscillations no anode current flows, means for applying to said electron tube an intermediate frequency whereby a modulated intermediate frequency wave is produced which is modulated in accordance with the modulation of the received signal Wave and whose frequency is a multiple of said applied intermediate frequency, and means for utilizing said modulated intermediate frequency wave.

13. A receiver according to claim 12, having means for impressing the intermediate frequency in phase opposition on the anode members, and an energy-deriving circuit tuned to double the frequency of the impressed intermediate frequency.

14. A receiver according to claim 12, having an energy-deriving circuit associated with said anode tuned to a harmonic of the lowest of said frequencies.

l5. A high frequency receiver comprising an electron tube having a split anode, an `oscillatory circuit yconnected symmetrically to this anode, a cathode cooperating with said anode, a source of current connected with said cathode, means for producing a magnetic field adapted to inuence the discharge space of said tube, the intensity of said magnetic field being of such a value that the rotation frequency of electrons under the influence of this eld equals the frequency of the received oscillations, means for applying to said anode a potential so related to the dimensions of said anode and the intensity of said magetic field that no anode current flows in the absence of received oscillations, a high frequency amplifying tube having a cathode, a brake electrode and a grid, means for biasing the electrodes of said amplifier tube for braking eld operation including means for applying a high positive potential to said grid, means for applying a signal to be received to said amplifying tube, and means for applying the output of said amplifying tube to said electron tube.

16. In a receiver according to claim 15, said amplifying tube having cathode, grid and brake electrodes and adapted to operate in brake field connection, a system of parallel conductors connecting said grid and brake electrodes and said split anodeand a receiving dipole connected symmetrically to this system.

17. A receiver according to claim 15, wherein said means for applying the output of the amplifier tube to the electron tube comprise two parallel conductors one of which connects said grid to one part of said split anode and the other of which connects said brake electrode to another part of said split anode, and wherein said means for applying signals to be received to said amplifying tube comprise a receiving dipole and symmetrical coupling means coupling said dipole to said grid and brake electrodes.

18. A high frequency receiver comprising an electron tube having a split anode, an-oscillatory circuit connected symmetrically to this anode, a cathode cooperating with said anode, a current source connected with said cathode, means for.

producing a magnetic field adapted to influence the discharge space of said tube, the intensity of said magnetic field being such vthat the rotation frequency of electrons under the inuence of said eld equals the frequency of the received oscillations, means for applying to the anode a potential so related to the intensity of said magnetic field and the dimensions of said anode that in the absence of received oscillations no anode current ows, means for applying to said electron tube an intermediate frequency whereby a current of said intermediate frequency modulated in accordance With the modulation of the received wave is produced, and means for utilizing said modulated intermediate frequency current.

19. A receiver according to claim 18, wherein the electron tube has a grid between the cathode and anode and a circuit interconnecting said grid and the cathode for receiving the intermediate frequency.

20. A receiver according to claim 18, having means for impressing the intermediate frequency in co-phasal relation on the anode members.

ERICH HABANN. FELIX GERTH. 

